There has been known a switch assembly, such as shown in FIG. 63 for example, as an electrical component for use in a bus-system network and the like which communicates a communication signal composed of a voltage signal by way of two bus lines. A switch assembly 1 comprises a pressing section 2, an operating shaft 3, an adaptor 4 and a communication-function incorporating contact 5.
The pressing section 2 accepts an operation given by an operator. The operator can change the state of the contact 5 by depressing the pressing section 2 in a direction of an arrow Y1. At this time, the operating shaft 3 shifts its position in association with the movement of the pressing section 2.
On the other hand, the communication-function incorporating contact 5 includes a switch section 7 serving as a switch for switching contacts. The switch section 7 is operated in conjunction with the operating shaft 3. Specifically, when the operator depresses the pressing section 2 in the direction of the arrow Y1, the operating shaft 3 is slidably moved in an direction of an arrow Y2 to depress the switch section 7 of the contact 5 in a direction of an arrow Y3 thereby changing the sate of the switch assembly 1. This causes the communication-function incorporating contact 5 to output a communication signal.
The adaptor 4 includes one contact mounting portion 9. This contact mounting portion 9 is capable of mounting a single contact.
FIG. 64 is a connection diagram in which the switch assembly 1 is connected to a network with a bus line BL by way of the communication-function incorporating contact 5 thereof. The communication-function incorporating contact 5 is connected to a CPU 15 via the bus line BL. The CPU 15 is adapted to receive an information communication signal issued by the communication-function incorporating contact 5.
The communication-function incorporating contact 5 outputs an ON or OFF signal depending upon the operation given by the operator. The CPU 15 receives this signal to control the operations of a motor M1 via another CPU 17.
The switch assembly 1 of such a configuration has the following drawbacks. Specifically, the switch assembly 1 with the communication-function incorporating contact 5 may be connected to the bus-system network so that an integral management may be provided for controlling the state of the switch assembly the same way as the other devices connected to the bus-system network are controlled.
However, the aforesaid switch assembly 1 is incapable of transmitting the operation of the operator directly to a target device. More specifically, the communication-function incorporating contact 5 is arranged as follows. When the operator manipulates a push button 11, the communication-function incorporating contact 5 transmits an information piece corresponding to the operation of the push button to the CPU 15 which is connected therewith. The CPU 15, in turn, issues a command to the device and the like.
If, at this time, the CPU 15 is disabled due to some abnormality, the operation given by the operator will never be transmitted to the target device. This leads to a disadvantage particularly when the power supply to the apparatus must be shut off in an urgent condition such as emergency stop.
On the other hand, it may be contemplated that a switch assembly incorporating no communication function is used instead of the switch assembly 1 with the communication-function incorporating contact 5 shown in FIG. 63. In a case where a plurality of switch assemblies of this type are disposed on an electric switchboard, wirings on a back side of the electric switchboard are as shown in FIG. 65. There is a problem that a large volume of complicated wirings is required for the connection of the individual switch assemblies.
In the general bus-system network, two bus lines (+V line and 0V line) are used, as the aforesaid bus line BL (see FIG. 64), for communicating the communication signal composed of voltage signal. The switch assembly 1 with the communication-function incorporating contact 5 is connected to such a bus-system network as shown in FIG. 66, for example.
As seen in FIG. 66, the circuitry of the switch assembly 1 is made up of the communication-function incorporating contact 5 (hereinafter referred to as “communications contact”) and a switch section 21. The communications contact 5 comprises an integrated communication circuit incorporating an input interface 22 (hereafter the interface is abbreviated as “I/F”), having a positive supply terminal Vin thereof connected to a positive +V bus line B1 as well as a zero-volt terminal Z and a ground terminal GND thereof connected to a reference 0V bus line B2. On the other hand, transmission terminals INP, INM of the communications contact 5 are connected to the both bus lines B1, B2. The communications contact 5 communicates the communication signal of voltage signal superimposed on the bus lines B1, B2.
By the way, the switch section 21 is connected to an input terminal Din of the input I/F 22. Manipulating the switch section 21 switches the level of the input terminal Din of the input I/F 22, thereby changing the operation mode of the communications contact 5. The switch section 21 conventionally employs a switch 21a of a contact-making configuration. A large capacitor 21b is connected in parallel with the switch 21a for preventing chattering at On/Off switching operations.
The switch 21a and the capacitor 21b constitute the switch section 21. It is noted that a reference character 23 denotes a pull-up resistor for the input terminal Din of the input I/F 22.
Unfortunately, if the switch section 21 comprises the switch 21a of the contact-making configuration, a high current need be conducted in order to ensure stable operations of the switch. This results in an increased amount of heat generation, which leads to a fear of degrading the quality or reliability of the component. Particularly where the switch sections 21 are collectively disposed, it is difficult to spare an adequate space for heat release and an even greater amount of heat generation results. Furthermore, the high current value constitutes a drawback of increase in the power consumption. In addition, the provision of the capacitor 21b for preventing the chattering results in an increased size of the switch section 21.
As shown in FIG. 66, it is a conventional practice to connect a surge-absorbing Zener diode 25 between the transmission terminals INP, INM for removal of surge noises invading the transmission terminals INP, INM of the communications contact 5 via the bus lines B1, B2.
In such a bus-system network, all the communications contacts 5 are connected in parallel with the transmission lines. Accordingly, the transmission path inclusive of the communications contacts 5 must have a small capacity in order to provide high-speed communications of communication signals of voltage signals between the plural communications contacts 5. Furthermore, it is preferred to limit the capacity between the transmission terminals INP, INM of the communications contact 5 to the minimum possible level in order to permit the greatest possible number of communications apparatuses to be connected to the network.
Unfortunately, a single Zener diode 25 is limited in the ability to accomplish the reduction of the capacity between the transmission terminals INP, INM. Thus, it has been impossible for a single Zener diode 25 to accomplish a sufficient reduction of the capacity of the transmission path inclusive of the communications contacts 5.
On the other hand, each of the communications contacts 5 must have a high impedance for holding a high impedance of the overall transmission path thereby ensuring that waveforms of the voltage signals as the communication signals are correctly communicated among the plural communications contacts 5 in the bus-system network. A coil is used as means for increasing the impedance of the communications contact 5. Particularly, an open magnetic circuit coil, which is less costly than a closed magnetic circuit coil, has conventionally been employed from the standpoint of cost-effectiveness.
The open magnetic circuit coil consists of a hollow bobbin and windings wound thereover. As shown in FIGS. 67, and 68, for example, an open magnetic circuit coil 27 is often disposed substantially at a center of an assembly body 28 or 29 of the switch assembly 1 incorporating the communications contact 5. In this case, the coil 27 is disposed in a manner that an axis of the coil 27 is in parallel with a direction orthogonal to a longitudinal direction of the assembly body 28 or 29.
However, the assembly body 28 or 29 with the coil 27 disposed substantially at the center thereof encounters the following problem. In a case where plural switch assemblies 1 individually incorporating the communications contacts 5 therein are arranged in juxtaposition, magnetic fluxes from adjoining coils 27 interfere with each other so as to cancel depending upon the orientations of the coils 27 as shown in FIGS. 67 and 68 (arrows in FIGS. 68 and 69 indicate the directions of the magnetic fluxes). As a result, the coils are decreased in inductance.
Therefore, the individual switch assemblies 1 must be juxtaposed as the communications contacts 5 spaced from one another to a degree that the magnetic fluxes from the adjoining coils 27 are kept out of interference. Otherwise, as shown in FIG. 70, the individual switch assemblies 1 incorporating the communications contacts 5 must be arranged in a manner that the adjoining coils 27 are positioned to direct the magnetic fluxes therefrom in orthogonal relation (as indicated by the arrows in FIG. 70) thereby keeping the magnetic fluxes therefrom out of interference. In either case, an increased installation space results.
It is a first object of the present invention to provide an electrical component, such as a switch assembly, which permits an integral management through network and contributes to space saving, and which permits the operation or the like given by the operator to directly affect the target device thereby ensuring the operation of the target device.
It is a second object of the present invention to provide an emergency stop system featuring more safe and reliable operations.
It is a third object of the present invention to accomplish an extended service life and reduced power consumption of switch means for use in a communications apparatus employing the above electrical component.
It is a fourth object of the present invention to reduce the capacity of the overall transmission path in the network by decreasing the capacity of the communications apparatus.
It is a fifth object of the present invention to achieve an increased impedance of the communications apparatus without increasing the size thereof.